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Topic: Another Paddleducks build log (Read 159529 times)

I have finally got round to making a start on my next ( Yep, I've caught it... ) project, and while tempted to do a Rocking engine, I had to stick with with my initial plan of building Bog's Paddleducks engine.

So I had previously got some materials gathered for this build, and not having any cast iron at all, but having a brass block that was itching to be reduced to a nice cylinder-shaped block, I decided to use brass for the cylinder.

Here is the raw brass block, the other dimensions are 25mm thick and 50mm high.

I then used my very expensive marking dye system and used my vernier caliper to mark out a rough shape to then transfer to my very expensive bandsaw (my right arm )

So I next ground up a tiny toolsteel for my tiny flycutter as per the Bogstandard curved profile that I read about on a thread here somewhere. This is my second attempt at grinding the curved shaped flycutter, I have a larger flycutter that doesnt cut as well as this latest attempt, practice I guess

So with this newly ground up tool I am totally impressed with it. The finish on brass is soo silky smooth!!! Compare it to using a end-mill and there is just no contest. I also learnt that my X2's Z axis is made out of a very tough but flexible form of spagetti. I am intending on re-inforcing the upright column, but in the meantime I have to be mindful of taking lighter cuts.

I have an even smaller flycutter, they're so dinky.

By the way, is there an accepted method of working out what speed to set the mill at for flycutting? ( the smaller flycutter seemed happy to run faster)

So after squaring and sizing the 4 sides I then squared off the 2 ends with a 4-flute mill.

It's amazing how the little brass chippings/shavings get everywhere (especially down the neck of my teeshirt, and they are pretty hot too ) My workbench was (and still is) covered with a golden snowstorm.

I then had to smooth the 2 ends with some 360grit wet+dry placed on a granite plate to try and get them to match the smooth flycutter-ed surfaces.

And here it is, the first part made to size (well within 0.02mm on 2 dimensions and dead on the 3rd )

That's all I got done today, not much to see so far, but it's good to be back on an engine project and I cant wait to get back into the workshop to crack on with it.

Tim

Edit: If you want to see larger versions of the pictures of this build click here

bogstandard

Seems like you have made a good start there Tim, best of luck following my ramblings.

Now there have been a few of these engines made, I can relax a little. At one time I was being innundated with emails for help where someone was having a problem, but now, people who have more up to date info can step in and help you as well if you need it.

Just go along nice and steady, do the measure twice, cut once routine, and don't worry too much if you haven't got the right materials, as long as it looks and feels strong enough to do the job, use it.You will find very few tolerances, any that are critical are well signposted. Just use the make it to fit rule, if you machine a slot a little too large, see if you can get away with fitting a larger piece into it. Lots of times, you will find it will save you having to make a new part.

With regards to the flycutter, as long as you have ground the faces as shown with the reliefs required, you should find that you will get a surface finish like a mirror with a finishing cut of about 5 thou on your particular machine.I have a heavy built machine and can take off 100 thou (2.5mm) in one go, and all I do is listen to the machine, it will tell you if it is struggling. I would suggest on yours for a max cut on non ferrous, about 20 thou (0.5mm) and on say a 3" total tip swing, try around 400 to 500 RPM and see how you get on. A lot of using a flycutter like this is feed rather than speed. The slower feed you go, the better the cut and finish.

With regards to the flycutter, as long as you have ground the faces as shown with the reliefs required, you should find that you will get a surface finish like a mirror with a finishing cut of about 5 thou on your particular machine.I have a heavy built machine and can take off 100 thou (2.5mm) in one go, and all I do is listen to the machine, it will tell you if it is struggling. I would suggest on yours for a max cut on non ferrous, about 20 thou (0.5mm) and on say a 3" total tip swing, try around 400 to 500 RPM and see how you get on. A lot of using a flycutter like this is feed rather than speed. The slower feed you go, the better the cut and finish.

Thanks Bogs, I have tried to grind the flycutter as per your C-o-C and photos, This second attempt seems to be better than my 1st go. I dont know if it is because of the flexibility of my little mill, but I seem to get a slightly better looking cut feeding from right to left, and I also note that I need to tram as the cutter is only leaving marks in one direction.

I found that I was removing about 0.3-0.4mm per pass, the mill didnt seem to mind that. I guess having a power feed would really help on getting a really good surface finish.( sigh, yet another mod to add to the ever-growing list) The flycutter tool tip swing is about 2" using this little flycutter.

I hope to get out to the workshop this afternoon to do a little more, (puts on best tv announcers voice) "Stay tuned for updates"

Tim

Logged

Measure with a micrometer, mark with chalk, cut with an axe - MI0TME

bogstandard

It is that slightly out of tram that you can use to your advantage with a flycutter.

Whichever way it is that does what is called the back cut, taking a tiny amount off, that is the way you should use for final finishing. It gives you two bites at it. Feed it so that the first cut is being done, but when the trailing edge that does the extra bit of cutting gets onto the face, slow down, and very gently carry on feeding. that back face is only taking off a minute amount, less cut than you could ever hope to put on with the handles, then just carry on until you have done the full cut. I find a little squirt of WD40, no matter what the material, really helps with getting that mirror finish.As you have said, having a rubber machine doesn't help, but with a little practice on using the fly cutter, your finishes will improve dramatically.

Whichever way it is that does what is called the back cut, taking a tiny amount off, that is the way you should use for final finishing. It gives you two bites at it. Feed it so that the first cut is being done, but when the trailing edge that does the extra bit of cutting gets onto the face, slow down, and very gently carry on feeding. that back face is only taking off a minute amount, less cut than you could ever hope to put on with the handles, then just carry on until you have done the full cut. I find a little squirt of WD40, no matter what the material, really helps with getting that mirror finish.As you have said, having a rubber machine doesn't help, but with a little practice on using the fly cutter, your finishes will improve dramatically.

Bogs

I seem to remember you saying that you used a slight out-of-tram mill as an advantage in finishing, thanks for reminding me of that.

Thanks Kvom for the advice to wait for the final finishing til after all the holes are bored, my excitement gets to me and I forget that I've got many more steps to do on the main block.

I got some time in the workshop today, and started out by Tramming my mill. A frustrating exercise as when you think it is in tram and then tighten the big nut holding the column in place, the act of tightening will throw the mill out of tram again.

After tramming the mill I started marking up the main block for the cylinder holes, then clamped the block in the vice on top of some 1/2" parallels. I then used the edge finder to locate the hole centres as accurately as possible, and then centre drilled them. Working out the graduations on the mills handwheels it worked out at 18 full turns to traverse from the center of one hole to the center of the other.

I then drilled and then opened out the holes starting with a 4mm drill, then 6mm, 7mm, 8mm, 8.5mm 8.7mm, 8.8mm, 8.9mm and then finally reamed the bores to 9mm. ( I would have drilled/reamed them 10mm but I dont have a 10mm reamer, but I do have a 9mm reamer so I figured that making the bores slightly smaller would not make a big difference. I'll just make the pistons to match )

And this is the end result.

I then turned (groan) to making the Top-Caps. I chucked up a length of some unknown steel ( to contrast with the brass ) in my 4jaw ( my 3jaw self-centering has too small a bore to allow the length to go into the headstock in order to use it without cutting it down ) Turned a section down to 18mm diameter, put a 9mm spigot on to fit the bore, then parted it off, and then repeated for the other.

Then I mounted my ER32 chuck, the 18mm collet and mounted the topcap in it to turn the "Top" side. The 2nd one turned out better, practice makes perfect better.

Because you were creeping up with the drills, you could have wacked the 10mm thru it. The surface finish would easily clean up with a bit of hand lapping.

Good to know for future reference thanks Bogs.

I do have to say that reaming this depth in brass was not as much fun as I thought it would be. Even though I snuck up with drilling it up to 8.9mm before using the 9mm reamer, it still would bind up and jammed up a couple of times. So I introduced my friends, the low speed pulley, the 3-in-1 oil can, and the "ream a little-back out a little to clear flutes-ream a little bit more". The only stuff that I've reamed before was thinner stuff, so it took me a bit to get used to getting the feed right.

Thanks Eric, It's great to be challenged with a more advanced build than the elmers #25. It feels good to be stretched and to learn new techniques.

And I have to say a really big Thanks to Bogstandard for taking the time to put together and write the plans for this, and then to make them available for free, that is truely great, and I really appreciate your time and effort that you put into this.

I reccomend everyone should download and read the plans, even if you are not considering building it the plans are very easy to follow and explain techniques that could apply to many other builds.

So we got a little bit more done today, I say we because Stefan (spynapples) was over finishing off his airgun-trigger part, once we got it finished he helped me out doing a little more on the Paddleducks engine.

1st of all we started on the packing nuts, we chucked up some 8mm hex brass bar, turned a 6mm section and then threaded it.

Then we parted it off and did the same again.

The only thing that bothers me a bit about these is that, because of the width of my parting tool there isnt much thread left, about 2.5-3 turns on each nut.

Then we cut off some 22mm round brass bar for the packing gland, chucked it up and turned down to 18mm. Then we turned down an 8mm section and put a center drill in the chuck and almost drilled it.

Then Stefan had to go so we called it a day there.

So just a short update, hopefully I'll get some more done over the weekend.

and ............. thanks for taking the time to do a complete write up,

You are more than welcome. I actually really enjoy doing the build log thing, it's good to try and explain and show what you've done, plus it is a really good learning experience as more experienced machinists will chime in with suggestions and helpful hints and tips ( or is that tints and hips )

I enjoyed the shop time this afternoon, first time turning stuff on the lathe (for me). Jolly addictive, and I'm glad I didn't reduce any of the parts to scrap. Thanks for letting me learn the basics on one of your projects, if I mess it up, you'll be able to tidy them up again!

Thanks for your help with my project too, it has made a world of difference!

Stefan

Logged

bogstandard

The steam gland screws shouldn't go all the way into the gland nut, as they are used to compress material in there. So after your first cut with your die, turn the die around and use the unmarked side. It should then cut the thread almost to the shoulder, as the die shouldn't have a lead in taper on the 'bad' side. If the die has a lead in on both ends, I usually grind down the die on the 'bad' side to get rid of the lead in, purely to allow me to cut a full depth thread right up to a shoulder.

I would suggest you grind up a specific undercut tool, about 0.02" (0.5mm) wide, as you will need it for all sorts of threading to a shoulder. Maybe not on this project, but for others in the future.

If you are single point cutting, you really need a small undercut to drop into anyway.

The steam gland screws shouldn't go all the way into the gland nut, as they are used to compress material in there. So after your first cut with your die, turn the die around and use the unmarked side. It should then cut the thread almost to the shoulder, as the die shouldn't have a lead in taper on the 'bad' side. If the die has a lead in on both ends, I usually grind down the die on the 'bad' side to get rid of the lead in, purely to allow me to cut a full depth thread right up to a shoulder.

I would suggest you grind up a specific undercut tool, about 0.02" (0.5mm) wide, as you will need it for all sorts of threading to a shoulder. Maybe not on this project, but for others in the future.

If you are single point cutting, you really need a small undercut to drop into anyway.

Bogs

Do you think I need to remake the gland nuts or is there enough thread on them? I can remake them as I havent yet drilled and tapped the packing gland (And it should remain concentric as it's mounted in an ER32 collet chuck that I can remove it in the ER32 chuck to turn up some new gland nuts using the 3jaw. (I'll make 4-5 nuts as Kvom mentioned that the valve packing glands are the same))

I'll grind up a specific undercutting tool too. I will be single point cutting on pretty much all the threads on this build as I have yet to make a tailstock die holder. I generally single point until near depth-of-thread and then clean up with a die.

Tim

Logged

Measure with a micrometer, mark with chalk, cut with an axe - MI0TME

bogstandard

The ideal method is to assemble the nut and gland together and tighten them up. Then drill the pair together to make a matched set. You might have to superglue the screw in, to stop it being unscrewed out when drilled from the other side, as really, you should turn the bore spigot and drill the central hole at the same time, to ensure that things are concentric to the bore. As shown on this bit of an article.

I personally would remake the screws, as you don't really have enough thread on there to hold the packing in position without the screw 'cocking over'. After you have drilled the thru hole, you can go back and countersink the top of the screw, and inside the gland itself, so that it forms the packing into a nice compact ball.

I am very impressed by the way you single point cut all your threads. I only do it when absolutely necessary.

If only everyone could pick up the technique, as you have, they would soon realise for those special one off's, there is no need to go chasing around the country for taps and dies.

I personally would remake the screws, as you don't really have enough thread on there to hold the packing in position without the screw 'cocking over'. After you have drilled the thru hole, you can go back and countersink the top of the screw, and inside the gland itself, so that it forms the packing into a nice compact ball.

I think that it'll be better to do like you say and remake the screws, I would have to make 2 more for the valve seals so I may as well churn out 4 ( or maybe one or 2 extra just in case the unthinkable happens and I make a tiny catastrophic mistake ) And as I'm at a point that I can interupt in the making of the packing glands, I may as well do the remake. That'll be the 2nd item to do tomorrow afternoon, 1st will be to grind up a thin grooving tool to make a more reasonably sized undercut for the threads.

Quote

I am very impressed by the way you single point cut all your threads.

Dont be that impressed, while I do find it enjoyable, I do it out of need as I dont have a way of holding a die on the lathe ( unless I handhold it gripped in a pair of vicegrips, but I somehow doubt whether I could create a square and parallel thread form that way ) I guess when I get around to making a tailstock die holder I will fall into the easier way of just using that, but until that time I have to do things the slightly harder way.

I generally single point most of my threads. I find it one of the most satisfying jobs to do on the lathe. Makes you feel really good when two parts spin together just right.

There is a great satisfaction to be found in single pointing a thread and then screwing on a commercially made nut or fitting, and seeing the 2 parts match up. But then again, there is great frustration in single pointing what you think is a M6 thread and then wondering why the M6 nut will only screw on about 1 turn, and the M6 die wont even attempt to go on square, and then realising that some idiot ( me ) has left the leadscrew gears set up for M5 thread , Or even more frustrating is finding out that the freshly cut thread has the proper depth of thread but that the overall diameter is just a fraction too big to screw in easily, and by some idiot's ( me again ) effort to screw said oversized thread in, the thread shears off in the tapped hole and then you have 2 parts to make again